Dark septate endophytic (DSE) fungi are widespread root-colonizing endophytes that play significant roles in host plant growth and adaptation. Ulmus pumila L., as a climax species in sparse forest-grassland ecosystems of sandy regions, contributes critically to regional ecological stability. In this study, root samples were collected from nine plots across three major sandy lands in Inner Mongolia—the Hulunbuir, Horqin, and Hunshandake Sandy Lands—to isolate and characterize DSE fungi. By combining traditional morphological classification with molecular identification, we determined the species composition, community structure, and spatial distribution of DSE fungi in U. pumila roots. Concurrently, key rhizosphere soil nutrient indicators were measured, and their relationships with DSE community distribution were analyzed to identify environmental drivers of DSE community assembly. A total of 200 DSE strains were isolated, which were classified into 16 species across 12 genera, 11 of which were identified to species level. Pure culture colonies exhibited diverse morphologies, predominantly black, dark green, or brown in color. DSE community composition differed markedly among sampling locations, with dominant species varying across sites. Pairwise similarity coefficients were all below 0.33, indicating substantial spatial heterogeneity. The Saihanwula site exhibited the highest colonization rate (22%). Soil total phosphorus (TP), total nitrogen (TN), and organic matter (OM) were identified as principal factors influencing DSE colonization rates, while soil moisture content (SMC), TN, and OM were key determinants of DSE community evenness. These findings provide a foundation for understanding root-associated DSE diversity in U. pumila and their ecological relationships with soil nutrient patterns in sandy ecosystems.
Ma et al. (Mon,) studied this question.